Process for polymerizing vinyl chloride



United States Patent 2,772,256 PROCESS FOR POLYNIERIZING VINYL CHLORIDEMichael A. Manganelli, Springfield, Mass, assignor to Monsanto ChemicalCompany, St. Louis, Mo., a corporation of Delaware N0 Drawing.Application August 13, 1953, Serial No. 374,123

10 Claims. (Cl. 260-923) This invention relates to a process for thepolymerization of vinyl chloride. More particularly, this inventionrelates to a process for preparing granular polyvinyl chloride that canbe rapidly blended with suitable plasticizers.

Polyvinyl chloride is used as a raw material in the preparation of awide variety of useful articles. It is conventional practice to preparepolyvinyl chloride by a suspension polymerization process, the vinylchloride being held in suspension by means of a heteropolymer of vinylacetate and maleic anhydride or maleic acid used alone or in conjunctionwith other conventional suspending agents. However, when polyvinylchloride is prepared in this manner using such conventional suspendingagents, the polymer is recovered in the form of relatively fine granuleshaving a substantially impervious surface. Such granular polymers arecomparatively dense and tend to blend with plasticizers at a slow rate,from 5 to minutes generally being required for blending operations. Ithas been recognized that porous granular polyvinyl chloride can beblended with plasticizers at a much more rapid rate but, heretofore, ithas not been possible to prepare porous granular polyvinyl chloride by asuspension polymerization process when using a heteropolyrner of vinylacetate and maleic anhydride or maleic acid as a suspending agent.

Accordingly, an object of the present invention is the provision of aprocess for the preparation of electrical grade polyvinyl chloride.

Another object is the provision of a process for the preparation ofgranular polyvinyl chloride that can be rapidly blended withplasticizers.

A further object is the provision of a suspension polymerization processfor the preparation of porous granular polyvinyl chloride wherein aheteropolymer of vinyl acetate and maleic acid or maleic anhydride isused as the suspending agent.

These and other objects are attained by polymerizing vinyl chloride inaqueous suspension in the presence of a polymerization catalyst, aheteropolymer of vinyl acetate and maleic acid or maleic anhydride andan ethylene oxide condensate of a saturated fatty acid mono-ester ofethylene glycol or glycerol, wherein the fatty acid residue containsfrom 12 to 24 carbon atoms and wherein the molar ratio of ethylene oxideto mono-ester is from 5:1 to 15:1.

Surprisingly, the granules of polyvinyl chloride prepared by thisprocess have a porous structure and, as a result, can be blended withplasticizers at a rapid rate (e. g. less than 4 minutes). Further, theplasticized polyvinyl chloride is a substantially homogeneouscomposition and only a relatively small percentage of unplasticizedpolyvinyl chloride particles are present.

Patented Nov. 27, 1956 The following examples are given in illustrationand are not intended as limitations on the scope of this invention.Where parts are mentioned, they are parts by weight.

EXAMPLE I Prepare seven batches of polyvinyl chloride (denominated l-7in Table I) by a suspension polymerization process. For each batch use100 parts of monomeric vinyl chloride suspended in 150 parts of watercontaining 0.25 part of lauroyl peroxide, 0.15 part of a heteropolymerof vinyl acetate and maleic anhydride and 0.2 part of the ethylene oxidecondensate set forth in Table I. The heteropolymer is prepared bycopolymerizing 1 part of vinyl acetate and 1 part of maleic anhydride insolution in 400 parts of benzene in the presence of 0.4 part of benzoylperoxide at a temperature of 50 C. for hours. In order to form polyvinylchloride, agitate each batch at a temperature of about 50 C. for aperiod of about 15 hours. At the end of this time recover the polymer byfiltration, wash with water and dry. The granular polymers of thedifferent batches will have varying degrees of porosity, the batchescomprising granular polyvinyl chloride having a high degree of porosity,capable of blending with plasticizer Within less than 4 minutes whenblended in accordance with the following test.

In order to test for porosity, blend .a plurality of samples ofpolyvinyl chloride from each batch with dioctyl phthalate in a Reedmixer at a mixer temperature of about 250 F., each sample consisting ofparts of granular polyvinyl chloride and 50 parts of dioctyl phthalate.In conducting the test, add the granular polyvinyl chloride to the mixerin the absence of plasticizer and malaxate until the polymer is heatedto about the temperature of the mixer. Then add the plasticizer. At 15second intervals withdraw a small sample of the material and press thesample against a sheet of filter paper with a spatula. When an oil-spotis no longer formed on the filter paper the plasticizer has beensubstantially completely absorbed by the polymer If an oil-spot is stillformed on the filter paper after an elapsed time of 4 /2 minutes,discontinue the test as the results are unsatisfactory. At the end ofthe test the plasticized polyvinyl chloride will still be in granularcondition and will feel dry to the touch.

In addition, test samples of the polyvinyl chloride from each batch forcolloidability (i. e. homogeneity). In order to do this, malaxate amixture of 100 parts of polyvinyl chloride, 50 parts of dioctylphathalate and 2 parts of glycerol mono-oleate (stabilizer) for 5minutes on a roll mill heated at C. Form this composition into sheetsabout 0.075 thick by pressing at C. for 2 minutes in a flash mold using1000 p. s. i. pressure. Measure colloidability by visually counting thenumber of fish-eyes (unplasticized particles of polyvinyl chloride)present in a given area of sheet. The sheets containing the greatestnumber of fish-eyes per unit of area have the poorest colloidability.Sheets prepared from batches 4 and 7 will contain a comparatively smallnumber of fish-eyes per unit of area While the sheets prepared frombatch 3 will be substantially free from fish-eyes.

The ethylene oxide condensate used for each batch and the results of theforegoing tests are summarized in the following table.

l The molar ratio of ethylene oxide radical (E) to mono-ester radical inthe ethylene oxide condensate of the mono-ester.

From the foregoing table it is seen that a satisfactory blending time ofless than 4 minutes was obtained only in the case of batches 3, 4, 5 and7 and that the blending time for batch 3 was appreciably lower than theblending time for the other satisfactory batches. Further, it is to benoted that batch 3 had excellent colloidability coupled with the mostrapid blending rate whereas the other satisfactory batches required alonger time for blending and did not possess such superiorcolloidability. The particle size of the granular polyvinyl chlorideprepared from the various batches has not been set forth. When blendingnon-porous granular polyvinyl chloride with plasticizers, particle sizeis of particular importance, but when porous granular polyvinyl chlorideis used, the size of the particles is not critical and need not beaccurately controlled. However, it is to be noted in passing that atleast 40% of the polyvinyl chloride of batches 1 through 7 will pass a100 mesh screen.

Porous granular polyvinyl chloride is prepared in accordance with thepresent invention by a suspension polymerization process wherein thevinyl chloride is suspended in water by means of a mixture of aheteropolymer of vinyl acetate and maleic anhydride or maleic acid andan ethylene oxide condensate of a fatty acid mono-ester of glycerol orethylene glycol.

The ethylene oxide condensates to be used in accordance with the presentinvention are the ethylene oxide condensates of mono-esters of fattyacids containing from 12 to 24 carbon atoms and ethylene glycol orglycerol. Porous granular polyvinyl chloride will not be obtained if themolar ratio of ethylene oxide to mono-ester is in excess of about 15 to1 or less than about 5 to 1. The fatty acids that may be used to preparethe monoesters are the lauric, tridecylic, myristic, palmitic, margaric,stearic, nondecylic, archidic, lignoceric, cerotic,

etc. acids.- Mixtures of ethylene oxide condensates of 7 ferred. Whenusing an ethylene oxide condensate of glycerol monostearate, especiallyan ethylene oxide con-- densate containing less than mols of ethyleneoxide per mol of glycerol monostearate, the most rapid blending rate andthe most satisfactory colloidability are obtained. It is preferable touse an ethylene oxide condensate containing from about 5 to 10 mols ofethylene oxide per mol of mono-ester when the fatty acid contains from12 to 18 carbon atoms and to use a condensate containing from about 10to mols of ethylene oxide per mol of mono-ester when the fatty acidcontains from 20 to 24 carbon atoms.

If porous granular polyvinyl chloride is to be obtained,

. from about 0.1 to about 0.3 part of ethylene oxide condensate shouldbe used for each 100 parts of monomer. For best results, it ispreferable to use about 0.2 part of ethylene oxide condensate per partsof vinyl chloride.

In order to obtain porous granular polyvinyl chloride it is necessary touse the above-described ethylene oxide condensates in conjunction with aheteropolymer of vinyl acetate and maleic acid or maleic anhydride. Ifsuspending agents other than such heteropolymers are used, the resultantpolymers will not have the desired porous structure. The heteroploymersmay be made by polymerizing mixtures of vinyl acetate and maleicanhydride or maleic acid in varying molar ratios, e. g. from 1:9 to9: 1. Usually, it is preferable to use maleic anhydride and to use aratio of maleic anhydride to vinyl acetate that does not exceed 1:1.Heteropolymers of this nature possess substantial solubility in waterwithout the use of compounds forming salts therewith. These suspendingagents are well-known compounds and may be prepared in accordance Withthe process describedin U. S. Patent No. 2,562,852 to M. Baer. Fromabout 0.1 to 1.0 part of heteropolymer per 100 parts of monomer shouldbe used.

In order to obtain a reasonably rapid polymerization rate, a suitableWater-insoluble, oil-soluble polymerization catalyst should be used.Among the catalysts that may be used are peroxides such as lauroylperoxide, benzoyl peroxide, ditertiary peroxide, acctyl peroxide,propionyl peroxide, toluyl peroxide, etc. Mixtures of two or more suchcatalysts may be used if desired. Preferably, from about 0.01 to about 1part of catalyst per 100 parts of monomer should be used. With respectto the amount of water, it is possible to'use from about 100 to 200parts of water for each 100 parts of vinyl chloride with satisfactoryresults. Preferably, about parts of water should be used for each 100parts of monomer.

The porous granular polymers that can be prepared by the process of thepresent invention are the homo-- polymers of vinyl chloride. Thepolymers have excellent: electrical resistance properties and areparticularly useful as electrical insulating materials.

will not be obtained.

What is claimed is:

1. A process for preparing a porous granular polymer which comprisespolymerizing 100 parts of vinyl chloride in suspension in from about 100to 200 parts of water containing from about 0.01 to 1 part of awater-insoluble, oil soluble polymerization catalyst and a suspendingmedium consisting of from about 0.1 to 1 part of a heteropolymer ofvinyl acetate and a compound taken from the group consisting of maleicacid and maleic anhydride and from about 0.1 to about 0.3 part of anethylene oxide condensate of a saturated fatty acid mono ester of acompound taken from the group consisting of ethylene glycol andglycerol, the fatty acid residue of said mono-ester containing from 12to 24 carbon atoms, said condensate having molar ratio of ethylene oxideto fatty acidmono-cster of from about 5:1 to about 15:1.

2. A process as in claim 1 wherein the hetero-polymer is a heteropolymerof equimolar proportions of vinyl acetate and maleic anhydride.

3. A process as in claim 1 wherein about 0.2 part of ethylene oxidecondensate is used for each 100 parts of When other ethylenicallyunsaturated monomers copolymerizable with: vinyl chloride are presenteven in small amounts (e. g. 90 parts of vinyl chloride and 10 parts ofVinyl acetate), the porous granular polymers of the present inventionz7. A process as in claim 6 wherein the ethylene oxide condensate is anethylene oxide condensate of glycerol monostearate.

8. A process as in claim 7 wherein the ethylene oxide condensate ofglycerol monostearate contains about 7 mols of ethylene oxide per mol ofglycerol monostearate.

9. A process for preparing a porous granular polymer which comprisepolymerizing 100 parts of vinyl chloride in suspension in about 150parts of water containing about 0.25 part of a water-insoluble, oilsoluble polymerization catalyst, about 0.15 part of a heteropolymer ofequirnolar portions of vinyl acetate and maleic anhydride and about 0.2part of an ethylene oxide condensate of glycerol monostearate, saidcondensate containing about 7 mols of ethylene oxide per mol of glycerolmonostearate.

10. A process for preparing a porous granular polymer which comprisespolymerizing 100 parts of vinyl chloride in suspension in about 150parts of water containing about 0.01 to 1 part of a water-insoluble,0il-soluble polymerization catalyst and a suspending medium consistingof from about 0.1 to 1 part of a heteropolymer of vinyl acetate and acompound taken from the group consisting of maleic acid and maleicanhydride and from about 0.1 to 0.3 part of an ethylene oxide condensateof a saturated fatty acid mono-ester of a compound taken from the groupconsisting of ethylene glycol and glycerol, the fatty acid residue ofsaid mono-ester containing from 12 to 24 carbon atoms, said condensatehaving a molar ratio of ethylene oxide to fatty acid mono-ester of fromabout 5:1 to 15:1.

References Cited in the file of this patent UNITED STATES PATENTS2,528,469 Condo et al. Oct. 31, 1950

1. A PROCESS FOR PREPARING A POROUS GRANULAR POLYMER WHICH COMPRISESPOLYMERIZING 100 PARTS OF VINYL CHLORIDE IN SUSPENSION IN FROM ABOUT 100TO 200 PARTS OF WATER CONTAINING FROM ABOUT 0.01 TO 1 PART OF AWATER-INSOLUBLE, OIL SOLUBLE POLYMERIZATION CATALYST AND A SUSPENDINGMEDIUM CONSISTING OF FROM ABOUT 0.1 TO 1 PART OF A HETEROPOLYMER OFVINYL ACETATE AND A COMPOUND TAKEN FROM THE GROUP CONSISTING OF MALEICACID AND MALEIC ANHYDRIDE AND FROM ABOUT 0.1 TO ABOUT 0.3 PART OF ANETHYLENE OXIDE CONDENSATE OF A SATURATED FATTY ACID MONOESTER OF ACOMPOUND TAKEN FROM THE GROUP CONSISTING OF ETHYLENE GLYCOL ANDGLYCEROL, THE FATTY ACID RESIDUE OF SAID MONO-ESTER CONTAINING FROM 12TO 24 CARBON ATOMS, SAID CONDENSATE HAVING A MOLAR RATIO OF ETHYLENEOXIDE TO FATTY ACID MONO-ESTER OF FROM ABOUT 5:1 TO ABOUT 15:1.